The present invention relates to a retractor for a vehicle safety restraint seat belt mechanism.
A seat belt restraint comprises a length of webbing which is arranged to pass across the torso of a vehicle occupant. The webbing is wound on a rotatable spool which is mounted in a retractor frame. The spool is biased in a webbing wound direction but is otherwise free to pay out webbing to accommodate normal movement of the occupant. In the event of a crash, the spool is locked against rotation and thus against further payout of webbing and the occupant is securely restrained against forward motion. Locking of the spool is effected by bringing a toothed locking pawl into engagement with a ratchet wheel fixed to the spool.
This invention relates to a method of assembling a ratchet wheel to a retractor spool and to an assembled retractor sub-component, and to an apparatus for performing the assembly method.
In high volume assembly lines different sizes of components are handled and this results in a variation in the amount of space between the components. This space is known as the end float and there is currently no way of accurately setting the end float control.
According to a first aspect of the present invention, there is provided means for fixing together two parts of a vehicle safety restraint retractor spool sub-assembly. The fixing means comprising providing plastically deformable formations on one of the ratchet wheels and one end of the spool and providing corresponding deforming formations on the other of the ratchet wheels and said one end of the spool.
The two parts of the sub-assembly to be fixed together may be, for example, a ratchet wheel and a retractor spool or a spring arbor and the spool.
The plastically deformable formations may be crushable ribs on axially extending pegs or self-locking deformable ears.
The corresponding deforming formations may be drafted holes large enough to accommodate the pegs but small enough to deform or crush the ribs. They will have essentially the same shape as the pegs and are preferably round. Alternatively, the deforming formations may be pegs that fit between the ears to deform them and lock the parts together.
The crushable ribs may be angled or straight sided and likewise the locking ears may have straight or angled inner edges.
The crushable ribs may have angled bottom and straight sides and may incorporate pips on each side of each peg.
An additional, self-locating peg may be provided on one part to aid assembly.
According to a second aspect of the invention, there is provided a retractor sub-assembly comprising a spool and a ratchet wheel, fixed together by co-operation between plastically deformable formations on one part and deforming formations on the other part. Additionally, the retractor sub-assembly may comprise a spring arbor fixed to the other end of the spool by co-operation between plastically deformable formations on one part and deforming formations on the other part. The arbor is pushed on until it is locked in position at a pre-set distance determined by other components such as a mechanism bush and the ratchet.
According to a third aspect of the present invention, there is provided a method of assembling a spool for a vehicle safety restraint retractor to a ratchet wheel. The method comprising of mounting a retractor frame on an assembly jig which has a spring loaded stop; mounting a spool in the frame by aligning the spool axis with the spring loaded stop; and pushing a ratchet wheel onto the end of the spool opposite to that contacting the stop until the ratchet wheel abuts the frame.